Financial Instruments Realized and unrealized gains (losses) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ (911)	$ (27)	$ 1,561	$ 312
Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(84)	0	(84)	0
Foreign Exchange Forward [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ (827)	$ (27)	$ 1,645	$ 312